Vehicles, including hybrid vehicles, have internal combustion engines that produce exhaust gases at a high temperature. The vehicle also may have various systems with waste heat that require cooling, e.g. the engine coolant system with coolant fluid. A thermodynamic cycle such as a Rankine cycle may be used to recover waste heat within the vehicle during operation and provide power to the vehicle using a heat exchanger. Due to the mixed phase of the working fluid within the heat exchanger, prior, conventional heat exchangers may result in uneven or non-uniform heating, thermal fatigue and wear, and vapor lock in the cycle.